1. Field of the Invention
This invention relates to a method of fabricating a semiconductor device such as a trench gate type of power MOSFET (Metal Oxide Semiconductor Field Effect Transistor).
2. Description of the Related Art
Power-use semiconductor devices, in which a power MOSFET is typically known, have a low on-resistance and a high-speed switching possibility, thereby being possible to effectively control a large current with a high frequency. Therefore, the power MOSFET serves as a small power conversion device, for example, as a power device used in personal computers.
A power MOSFET is a semiconductor chip having a semiconductor substrate; an epitaxial growth layer formed thereon; and a plurality of cells formed in the epitaxial layer to be coupled with each other. In a trench gate type power MOSFET, cell gates are buried in a trench and coupled to each other. The trench gate pattern is formed by use of micro-fabrication technologies and size controllability thereof is important.
To form a certain pattern by use of a micro-fabrication technology within semiconductor device fabricating processes, it is desired to improve the size controllability, and this is not limited to the trench gate pattern case. For example, there has been provided a method of forming a contact hole with a certain pattern in an interlayer insulating film with a high uniformity and a high reproducibility (refer to Unexamined Japanese Patent Application Publication No. 2001-351896). There has also been provided a method of forming a trench pattern in an insulating film in such a manner that bottom thereof is set at a certain position (refer to Unexamined Japanese Patent Application Publication No. 2003-324102).